Electromigration (EM) is the transport of material caused by movement of ions in an electrical conductor due to momentum transfer between conducting electrons and diffusing metal atoms. The effects of EM are important in applications where high current densities are used, such as in the microelectronics industry. For example, as the size of electronic structures, such as integrated circuits (ICs) decreases, the effects of EM increase.
A particular EM effect is a reliability decrease of semiconductor chips or other ICs. EM may also cause the eventual loss of electrical connections or failure of a circuit. Although EM damage may ultimately result in the failure of the IC, some IC may exhibit seemingly random errors prior to the failure. In a laboratory setting, EM failure may be seen utilizing an electron microscope. With increasing miniaturization of electronic components, the probability of failure due to EM increases due to increasing power density and current density.
In some semiconductor manufacturing processes, copper has replaced aluminum as the interconnect material of choice. Though copper is more fragile, it has become preferred for its superior conductivity and lower susceptibility to EM effects. However, EM continues to be an ever present challenge to the semiconductor device fabrication industry.
Recently, three-dimensional integration of integrated circuits with through-silicon-vias (TSVs) has been used by the semiconductor industry for achieving enhanced electron device capabilities. TSVs create electrical paths through the entire silicon substrate. Such structures and associated processes present a new challenge for EM reliability of surrounding BEOL interconnects.